Nickel-aluminum layered double hydroxide as a nano-sorbent for the solid phase extraction of selenium, and its determination by continuous flow HG-AAS

We have used a nano-structured nickel-aluminum layered double hydroxide (Ni-Al LDH) for the extraction of trace levels of selenium prior to its determination by continuous-flow hydride generation atomic absorption spectrometry. Extraction is based on the adsorption of Se(IV) anions on the Ni-Al-nitrate LDH, and/or their exchange with the nitrate anions in the LDH interlayer. The effects of pH value, amount of nanosorbent, eluent type and concentration, sample volume and flow rate were optimized. No appreciable matrix effects were observed. Under optimum conditions, the limit of detection (defined as three times the standard deviation of the blank signal divided by the slope of the calibration plot) is 10 pg mL(-1), and the relative standard deviation is 2.8 %. The sorption capacity and preconcentration factor are 10 mg g(-1) and 33, respectively. The method was successfully applied to the determination of Se(IV) in tap water, river water, well water, wastewater and oyster tissue (certified reference material, CRM 1566b).